Telephone system.



A. H. DYSON. TELEPHONE SYSTEM.

APPLICATION FILED FEB- s. 1905. RENEWED APR. 19. 1906.

1,148,66Q. V Patented Aug. 3, 1915.

Q 3 SHEETS-SHEET 1.

A. H. DYSON.

TELEPHONE SYSTEM.

, I905. RENEWED APR. 19,1906.

APPLICATION FILED FEB- 6 Patented'Aug. 3,1915.

3 $HEETS--SHEET 2- IIVVLYVTOR.

A. H. DYSON.

TELEPHONE SYSTEM.-

APPLICATION FILED FEB-6.1905. RENEWED APR. 19.1906.

1,148,665. Patented Aug. 3,1915.

3 SHEETS-SHEET 3- W l I YVELSLS: IN V EN '1 OR.

if) W7 /%mzz/V UNITED STATES PATENT OFFICE.

ALFRED BL DYSON, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNPE ENTS, TO KELLOGG SWITCHBOABD AL SUEPLY COMPANY, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented'Aug. 3, 1915.

Application filed February 6. 1905, Serial No. 244,379. Renewed April 19, 1906. Serial No. 312,663.

To all whom it may concern:

Be it known that I, Anrnrn H. Drsox, a citizen of the United States, and resident of Chicago, county of Cook, and State of H11- nois, have invented new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates particularly to telephone exchange systems in which the connection of subscribers lines is secured by automatic mechanism at the central oflice actuated under control of switching mechanism at subscribers stations A feature of my invention consists in introducing between two automatic switches, used in establishing a connection, auxiliary apparatus and circuits adapted to accomplish the usual inter-action between said switches, employing two conductors only for accomplishing the said inter-action.

In the systems which I have had especially in mind in developing my invention, three or more conductors between switches are used in performing the usual functions of the switches, and my invention, when applied to trunking ems between exchanges, obviates the necesity of extending these three or more conductors from one exchange to the otherand thus allows a. considerable in the expense of installingtrunking circuits between exchanges In the automatic telephone exchange systems referred to, there is provided for each switch a release magnet operated, upon the establishment of an earth connection by mechanism associated with another switch. In case two switches used in establishing a connection are in difierent exchanges, the earth connection used in performing the release operation might of a potential different from that of the earth at-the exchange where the switch to be released is located, and the release operation might be rendered unreliable on account of this dilferencc of potential. I therefore provide, in connection with my invention, means whereby I eliect the release of each switch used in making a connection from an earth connection mtablished at the exchange in which the switch is located.

These and other features of my invention will up or at length in the following detailed ifscription.

Referring to the drawings, I show in Figure 1, consist of Sheets 1 and 2, a symbolical illustration of two subscribers lines with automatic telephone exchange switchboard apparatus and trunking apparatus arran ed in accordance with my invention. In I ig. 2, I show an automatic switch adapted to be used in connection with-the circuit arrangement shown in Fig. 1- Reference will be made in the detailed description of F 1g. 1 to certain mechanical features and movements of this switch, which is to be re gardedas typical and generic, for the purpose of illustrating concretely mechanical forms which the work to bedone by certain parts of Fig. 1 may uire. Fig. 2, Fig. 2, Fig. 2, Fig. 2 and Fig.2 illustrate vari- 0115 details of the structure shown in 2.

The automatic telephone system disclosed in Fig. l is operated by step-hy-step mechanism at the central ofiice, the movement of said mechanism being directed by switching mechanism at subscribers stations At F and K, I have shown this Substation switching mechanism as consisting ofia pair of simple keys, but it will be understood that in practice subscribers are provided with call sending devices which efi'ec't the switching movements necmsary for completing and destroying a mnnection without requiring from the: subscriber the amount of attention and care which would be required to prevent mistakes if the actual apparatus illustrated were used. In the system illustrated, each subscribcrsline terminatesin a switching mechanism at the central oilice, individual to it. These individual switches (ordinarily called first selector switches) are provided with wipers, mounted upon a. shaft, which may be" placed, under the control of the subscriber towhom the switch is individual, in electrical connection with terminals of secondary switches which are common for connection to a. certain group of subscribers. Means are provided whereby, after a calling subscriber has caused the wipers of his first selector switch to be placed in engagement with the terminals of a secondary switch (in the system shown, ordinarily called a. second selector switch the subscriber is then enabled to direct stepby-step movement of such second selector switch. The second selector switch is pro vided with wipers which are adapted, under the control of subscribers, to be placed in engagement with terminals of tertiary switches (in the system shown, ordinarily called connector switches) which are common for connection to a certain group of subscribers. When the subscriber has placed his first selector switch in electrical connection with the second selector switch and then has placed the second selector switch in electrical connection with the connector switch, he is enabled to direct the movements of step-by-step mechanism of the connector switch in such a manner as to cause wipers, forming terminals of the said connector switch, to engage contact points which form the terminals of any individual subscribers line in the group to which the connector switch is common for connection.

The system, which I have shown, may be used for telephone systems having several thousand subscribers, and subscribers lines may terminate in one exchange or may be difidedamong several exchanges. In the system'as shown, a connector switch would be common for connection to the lines of a hundred subscribers, and a second selector switch would be common for connection to a thousand subscribers. In other words, the wipers of a second selector switch are adapt; ed, under the control of subscribers, to placed in electrical connection with terminals of connector switches arranged in ten groups, the connector switches of each group being common for connection to one hundred subscribers The numerical'ratios given are arbitrary and, practice, may be varied to suit special uirements.

I have sh d wn in Fig. 2 an automatic switch mechanism of a type well known in the art, but it'is to be understood that my invention does not consist in providing means for operating switches of this type in particular, but that switches of any approved construction may be employed.

I show in Fig. 1 :2 plfialllity oieglectromagnets, a then 0 w 'c is n especiahy for actg mplishing circuit changes, and a portion of which is used for eifecting movements of the main shafts of the automatic switches. In the following detailed description, I- shall refer to electromagnets of the former class as relays and to those of the latter class as magnets.

Where I have shown, in Fig. 1, armatures associated with electromagnets, it is to be understood that the armatures, as illustrated, are in their normal positions. 'hen the electromagnets with which they are respectively associated are energized, the ar' matures will'be attracted; and upon subsequent dcnergization of the electromagnets with which they are respectively associated, thy will return to their normal positions 55 Thecircuit changes, accomplished by the energization of the said electromagnets and by the attraction of their armatures, may be readily understood from the illustration, and detailed description of their exact operation in each case is thought to he unnecessary.

While my invention is described in the following as employed for providing trunking facilities between two exchanges, I do not limit myself to that particular application of my invention, as it is of general application and may be applied in a variety of ways Referring first to Fig. 2, I show a shaft 27, the upper portion of which is provided with orizontal ratchet teeth, below which are provided vertical ratchet teeth. The said shaft is adapted to be moved vertically and with a rotary motion with respect to the banks of contact points 284 .and 285. Upon the shaft are rigidly mounted two pairs of wipers 258 and 259 which, when the shaft is raised and turned, are adapted to be placed in contact with pairs of contacts shown in banks 284 and 285, respectively.

Referring to Fig. 2, the structure of the rows of contacts may be readily understood. It will be noted that each bank of contacts consists, as illustrated in Fig. 2, of one hundred pairs of contacts arranged in vertical and horizontal rows of ten pairs each.

The mechanical operation of the svfitch is as follows: When magnet 271 is energized, its armature 272 is attracted and pawl 290, being mounted upon said armature, engages a tooth of the horizontal ratchet and raises the shaft onestep up. Armature 27:2 is provided with'arm 291 which, upon the first energization of magnet 271, raises arm 26*, thereby disengaging it from the pin shown in the illustration upon dog 292 which latter thereupon moves toward the shaft and engages with its upper portion a tooth of the horizontal ratchet, maintaining shaft 257 in whatever position it may have been raised vertically by pawl 290. Armature 272 is also provided with arm 293 which, upon the first attraction of the said armature, lifts arm 265 out of engagement with the pin shown upon armature 282 of magnet 281, thereby releasing pawl 266 and rendering the said pawl movable when magnet 276 is operated. If a number of successive energizing impulses is imparted to the ener gizing winding of magnet 271. shaft. '25? will be moved upward by the engagement of pawl 290 with the successive teeth of the ratchet it is adapted to engage, a nannber of steps corresponding to the energizing impulses imparted to the magnet. dog 292 maintaining the shaft in its raised position after each step.

Magnet 278 is adapted, by means of pawl 279 mounted upon armature 297, to effect a rotary movement of shaft 257 by causing the engagement of said pawl upon the energizat-ion of said magnet, with the vertical ratchet teeth of the shaft, moving pairs of wipers 25S and 259 with a rotary movement from left to right. Successive energizing impulses sent through the magnet 278 effeet, by means of the said pawl 279, succemire rotary movements of the shaft. The lower portion of dog 292 is adapted to en gage, when the dog is disengaged as above described, the vertical ratchet teeth on the shaft and maintains the shaft in whatever rotated pom'tion it may be placed by successive energizations of magnet 278.

Referring now to magnet 2T6; upon its armature 277 is mounted a ratchet consisting of teeth 273, 274 and 275. When armature 27? is attracted by the energization of the magnet, the ratchet mountedthereon is drawn downward with respect to pawl 266, and upon the release of the armature the said pawl moves out of contact with tooth 273 and forward into contact with tooth 27- The said pawl being pivoted and rigidly attached to arm 267,. the said arm thereby is moved out of contact with contact point- 268 upon which it normally rests and into contact with contact point 269, and a second attraction and release of armature 27'? again causes the forward movementof pawl 266, mo\-' arm 26? into engagement with contact point 270. It will be noted that in case magnet 276 isrin anunenergized condition, each successive energizetion of magnet. 278 will cause a forward movement of pawl 266 by means of arm 280 mounted on the armature of magnet 27S and en aging armature 277 of magnet 276 Tooth 2T5 prerents further forward movement of pawl 266 when said pawl engages said tooth There being-ten horizontal ratchet teeth adapted to be medefor securing vertical,

movements of the shaft .andten =ver'tical ratchet teeth adapted to be used for securingrotary movements of the shaft, the pairs of wipers 25S and 259 may be placed in contact with any correspondingly placed pairs of contacts in banks 284 and 285 by sending suitable numbers of energizing impulses through magnets 271 and 278. Assuming that said wipers have been placed in contact with desired pairs of contacts in the said banks, the return of the wipers to their normal position. as shown in the illustration, is secured by the energiZat-ion and deenergization of magnet 281, in the following manner: The energization of the said magnet attracts its armature 282 which moves forward arm "264 pivoted upon said armature in such a manner that it engages the pin upon dog 292; at the same time, the pin upon said armature 282 engages the offset on arm 265. Upon the de'e'nergization of magnet 281, its armature is moved away from the core of the magnet by spring 283 which operates to draw do" 292 out of contact with the ratchets of the shaft and retains it in its withdrawn position. At the same time, arm 265 is drawn backward and, being. pivoted to pawl 266, returns the said pawl to its normal position, as shown in the illustration. The withdrawal of dog 2-92 out of engagement with the ratchets upon shaft 257 allows the free movement of the shaft, and the torsion of spring 262 turns the shaft with a rotary motion opposite to that effected by pawl 279. TVhen this motion has placed wipers 258 and 2-59 out of engagement with the last pairs of contacts to the left of banks 284 and 285, shaft 257 is moved downward by gravity and rests in its normal position shown in the illustration.

Referring to Fig. 2, I show a plurality of arms associated with pawl 266 of which arm 267 is adapted to engage contact points 268, 2-69 and 270, the other arms being adapted to engage the other series of contact points mounted in association with those designated, respectively. This'figure discloses means by which pawl 2266 upon its movement may be adapted to effect a plurality of simultaneous circuit changes. It is evident that the number of circuit changes so efiected may be varied as required.

Referring to Fig. 1, consisting of Sheets 1 and 2, I show at F substation apparatus consisting of key 5 with its associated anvils 4 and 6 controlling the circuit of limb P of the telephone line, key 2 and its associated anvils 1 and 3 controlling the circuit of limb S of the telephone line, transmitter 7, induction coil 1Q, receiver 14, book lever 13, hell 9 and condenser 8. At A I show circuits apparatus in diagrammatic form of a first selector switch associated with the line of subscriber F; at B, trunking apparatus and circuits connected by limbs G and H of atrunk circuit with a second selector switch C assumed to be located in an exchange other than that in which switch A and trunking apparatus B are located; at D, I show a connectorswitch and circuits adapted to cooperate with second selector switch C'in establishing a con nection; at K, I show subscribers station apparatus similar to that shown at F: and at E, a first selector switch associated with the line of subscriber K, similar to that shown at A. Referring to the trunking apparatus and circuits shown at B. 30, 32, 42 and 44 represent contact points forming the terminals of the trunk circuit. These terminals are located in contact banks amociated with first selector switch A. and are multipled to other first selector switches. Relay 71 has its winding normally legged to battery 81 from limb H of the trunk circuit through contact 83-88. W'hen the said relay is energized, it attracts its armatime which causes spring 76 to break its normal engagement with spring 77 and to engage spring 80, and also causes spring 73 to move toward spring 74 associated with relay 72. Relay 72 has its winding normally legged to battery 81 from limb G of the trunk circuit through contact 84-85. When energized, it attracts its armature, causing spring 78 to break its normal engagement with spring 75 and to engage spring 80, and also causes spring 74 to more toward spring 73. If the two relays 71 and 72 are simultaneously energized, the attraction of their armatures will cause the ends of springs '73 and 7-1: to engage. Relay 82 has its winding normally bridged between limbs G and H of the trunk circuit, its circuit being traced through contacts 93-98, 77-76, and 75-78. When the said relay is energized, its armature's 8,3 and 84 engage respectively anvils S7 and 86 and disengage anrils S8 and 85, thereby disconnecting the windings of relays 71 and 72 from limbs H and G of the trunk circuit. Relay 97 is difierentially wound and, when its core is magnetized, attracts its armatures, closing contact 95-96 and opening contact 93-98. The opening of the latter contact breaks the circuit of relay 82. Condensers 89 and 90 are introduced into limbs G and H of the trunk circuit respectively, at points intermediate of the connections to said limbs establishing the bridge of relay 82 and the connections from the hmlte'7 to the winldin 0 re ays I an 1,; respective y. Lifibs G and H of the trunk circuit terminate at second selector switch C in circuit changing arms 135 and 132, respectively. c

In the following detailed description, I shall amume that the horizontal rowsof contacts designated 0 and c in Fig. 2 are (regarding Fig. 2 as a firstselector switch) terminals of ten trunk circuits asociated nth second selector switches located in an exchange wherein terminate lines of suhscribers numbered from 5000 to 5999. I further manic for purposes of description that subscriber F desires to be connected with subscriber 5436. To accomplish this, subscriber F depresses and releases key 5 fire separate times, thereby sending five impulses of current over limb P of the telephone line over the following path: from ground through contact 6-5, over limb P of the line, through contact 3-2-02, through the winding of relay and to battery 52, thereby causing relay 45 to attract and re lease its armature 46 five times. Each attraction and release causes an impulse of current over the following path: from ground 51 through contact 46-47, through contact 60-62, through contact 24-25, through the winding of magnet 23 and to battery 22, thereby causing five successive energizat-ions and deenergizations of the said magnet 23. This magnet corresponds to magnet 271 (Fig. 2) and the energizations and deiinergizations thereof described cause shaft 257 (Fig. 2) to be raised upward five steps by the engagement of pawl 290 with successive horizontal ratchet teeth of the said shaft, which places pairs of Wipers 258 and 259 in positions horizontal with rows of contacts a and 0 Referring to Fig. 1, the first upward step of the shaft grounded contact 37 by means of anvil 36, thereby rendering the first selector switch busy and preventing connection being made with the line of Subscriber F by any other subscriber. Subscriber F now depresses key 2 to make contact with anvil 3 and releases it. An impulse of current thereby results over the following path: from ground through contact 3-2, over limb S of the line, through contact 55-56, through the winding of relay 49 and to battery 52, thereby causing the energization and denergization of relay 49. Armature is attached and released, thereby causing the energization and denergization of relay 59 by a momentary impulse of current flowing over the following path: from ground 51 through contact 50-48, through the winding of re lay 59 to battery 70. Relay 59 corresponds to relay 276 (Fig. 2) and its energization and denergization, as described with reference to said Fig. 2, moves pawl 266 out of engagement with ratchet tooth 273 and into engagement with ratchet tooth 274. Referring to Fig. 1, this accomplishes the following circuit changes: Ann 19 is moved into engagement with contact point 20; arm 24 is moved into engagement with contact point 26; arm 33 is moved into engagement with contact point 3%; arm 38 is moved into engagement with contact point 39; andarm moved into engagement with contact point 57. Magnet 15 is energized upon engagement of arm 19 with contact point 20, by current over the following path: from ground 18, through contact 19-20, through the Winding of said magnet, through contact 17-16 to battery Magnet 15 corresponds to magnet 278 in Fig. 2, and the attraction of its armature moves shaft 257 (Fig. 2) with a rotary motion, by the engagement of pawl 27 9 with the vertical ratchet of the said shaft, one step, so that pairs of wipers 258 and 259 rest in engagement with the first pairs of contacts at the left of rows 0 and 0. These pairs of contacts are multipled to other first selector switches and in case multiples of the first pairs are already in use, the contact of the said pairs corresponding to contact 32 (Fig. 1) will be grounded and relay 59 will be again energized and (referring to Fig. 2) said relay corresponding to relay 276 will prevent the movement of pawl 266 into engagement with ratchet tooth 275 until the said relay is denergized.

Referring to Fig. 1, the circuit of magnet 15 is a make and break circuit and the magnet alternately is energized and denergized as long as arm 19 tests in contact with contact point :20. Each energization of the said magnet moves the shaft one step with a rotary motion, wipers 25S and 259 engaging with each step successive airs of contact points in rows 6 and c ig. 2) until pairs are reached in which the contact corresponding to contact 32 in Fig. 1 is ungrounded or idle. This is assumed to occur when wipers 29, 31, 41, 43, engage respectively contacts 30, 32-, 42, 44. As soon as this occurs, relay 59 in Fig. 1 is deenergized and, referring to the corresponding relay 276 in 2, pawl 266 moves into engagement with ratchet tooth 275. The followiug circuit changes thereby result (referring to Fig. 1): Arm 19 is moved into contact with contact point 21, thereby preventing further energization of magnet 15; arm 24 is moved into engagement with contact point 2?; arm 33 is moved into engagement with contact point 35, thereby throwing grolmd upon contact 32 associated with the trunk circuit selected and its multiples, and rendering the said trunk circuit busy with respect to other subscribers; arm 38 is moved into engagement with contact point 40, and arm 55 into engagement with contact point 58. Subscriber F has now selected an idle second selector switch in an exchange other .than that in which his telephone line termi hates, the said second selector switch being associated with and adapted to be used in establishing connection with lines of subscribers numbered from 5000 to 5999. The second selector switch C may be of similar construction to the first selector switch A. The horizontal rows of contact points in banks 28-1 and 285 in Fig. 2 (regarding said Fig. 2 as a second selector switch) are terminals of connector switches adapted to be operated to select and establish connection with individual subscribers lines, numbered as above specified. For pm- -of description, I assume that the horizontal rows of contacts, designated d and d in banks 281 and 1285 (regarding Fig. 2 as a second selector switch) are terminals of ten connector switches adapted to be operated to select and make connection with lines of subscribers numbered from 5400 to 5199. Subscriber F now depresses and releases key 5 four times, thereby closing current over the following path: from ground, through contact 65, over limb P of the line. through contact 3H0, through contact 4:1.-12,through contact 8M5, through the winding of relay 72 and to battery 81. This flow is in four impulses. and relay 72 is energized and deenergized four times. Each energization and denergization eflects the attraction and release of its armature and causes an impulse-of current to flow over the following path: from ground 79, through contact between springs and 78, over limb H of the trunk circuit, through contact 132-07, through winding of relay 101 and to batterylOO, thereby energizing and denergizing relay 101 four separate times. Each energization and denergization of relay 101 causes an impulse of current, through contact 105103, through magnet 115 to battery 119, energizing and denergizing the said magnet four times. The magnet 115 corresponding to magnet 271 in Fig. 2, the wipers of the second solector switch C are raised upward four steps and are placed in a position horizontal with respect to the horizontal rows of ,contact points d and d (Fig. 2). Subscriber F now depresses key 2 and releases it, thereby causing an impulseof current to flow over the following path: from ground through contact 32, over limb S of the telephone line, contact 55-58, contact 43'1- 1, contact 83-88, through the winding of relay 71 to battery 81, thereby causing the said relay '51 to be energized 'and deenergized. This energization and denergization causes an impulse of current to flow over the following path: from gr0und ;79, through contact between springs 8.0 and .76, over limb G of the trunk circuit, thro ugh contact 135-08, through the winding of .re-

lay 102 and to battery 100. This impulse ener izes and deenergizes relay 102, attracts ing and releasing its armature and causing an impulse of current over the following path: from ground 107, through contact 106-404, through the of relay 138 and to battery 1,12. .1Rclay138 corresponding to relay 27 6 .2, and magnet 108 cortespondingsto magnet 278 in Fig. '2, the shaft of-the-second selector switch is rotated in a manner similar to that described with reference to the first selector switch :1, until its wipers are placed in engagement .with contact points which are the terminals of an idle connector switch asociated 'with the desired group of subscribers This is assumed to occur when wipers 124, 126,128, 130-engage respectively contacts 125, 127, 129, 131. When this occurs, relay 138 will be denen gized and arms 111, 116, 1'21, 132 and I35 will be moved respectively into engagement with contact points 113, 118, 123, 134 and 137.

Fig. '2 may be regarded as illustrating connector switch D with the change that the rows of contacts in the upper bank 384: may be news of single contacts instead 'of arranged in pairs, and one of the wipers of pair 258 may be omitted. Ann 280 is omitted.

Regarding Fig. 2 now as illustrating the connector switch selected as above described, the third horizontal rows of contacts from below in banks 284 and 285 are assumed to be the terminals of the subscribers lines numbered from 5431 to 5440. Subscriber F now sends, by means of key 5, three impulses of current throuagll; the winding of relay 72 in the manner eady described. In this case,the three energizatious and denergizations of relay 72 establish impulses of current over the following path: from ground 79, through contact between springs 80 and 78, over limb H of the trunk circuit, contact 132-134, contact- 128-129, contact 165- 166 through the winding of relay 145 to battery 143. These impulses of current cause the energization and denergization of relay 145 three times and, its armature being attracted and released three times, three im pulses of current are caused to flow over the following path: from ground 144, through contact 147-150; through contact 195194, through contact 19909, through the winding of magnet=-197 to battery 198. Magnet 197 in the connector switch corresponding to magnet 271 in Fig. 2, the shaft of the connector switch is raised three steps upward, placing the wipers of the said switch in a position horizontal with the third rows of contacts in banks 28431111 285. Subscriber F now sends one impulse of current over limb S of the telephone line through the windiug o'f relay 71in the manner already described; The armature of the said relay is attracted and released, which causes an impulse of current over the following path: 79, through contact between springs 76, over limb G of the trunk circuit, contact 135137, contact 130-131; the winding of relay 146, through contact 163 -168 to battery 171. Relay thereby energized and denergized and attracts and releases its armature. causing an of current to flow over the following path: from ground 1 1-1, through contact lei -151, through the of'rclayr192'to battery 196. Relay 192 relay 27cm Fig. 2 and its energization and denergization, due to the above flow of current, causes pawl 266 to be moved-out of engagement with ratchet tooth 273 and into engagement with ratchet tooth 274;aocomplishing (referring to Fig. 1) the following circuit changes: Arm 199 is moved. into engagement with contact point 200; arm 20?!- is moved into engagement with contact point 203; arm 211 is moved into en gagement with contact point 212; and arm 215i5'jn0vad into engagement with contact point .216. Subscriber F now causes, by means -of key 5, six impulses of current to flow through relay 72, which causes relay 145 to be energized and denergized six times in the manner already described. The armature of relay 145 is attracted and released six times and causes six impulses of current flow from ground 14-1, through contact 199200, through the magnet 281 to battery 198. Magnet 281 corresponding to magnet 278 in Fig. 2, the six impulses of current above described cause shaft 257 (Fig. 2) to be rotated six steps, which brings the wipers of the switch into contact with the sixth contacts in banks 28- and 285, counting from left to right, of the third horizontal rows from below which contacts are the terminals of the line of the desired subscriber No. 5436. This (referring to Fig. 1) means that wipers 205, 207 and 209 are placed in engagement with contact points 206, 208 and 210 respectively, which are terminals of first selector switch E of subscriber K. Subscriber F now de resses and releases key 2 once, thereby sen ing an impulse of current throu h the winding of relay 71 energizing and deiinergizing the said relay and causing the attraction and release of its armature This causes an impulse of current to How from ground 79 over limb G of the trunk circuit, through the winding of relay 146 to battery 171. The armature of relay 146 is attracted and released. In case the line of K is already in use, contact point 206 will be grounded and an impulse of current results over the following path: from grounded contact point 206, wiper 205, through contact 202203, through contact 148-153, through the winding of magnet 185 to battery 189. This impulse causes the energization and denergization of the said. magnet. Magnet 185 corresponding to magnet 281 (Fig. 2), its energization and denergization causes the withdrawal of dog 292 (Fig. 2) from engagement with the ratchets of shaft 257, and allows the shaft to return to its normal position in the manner previously described. Paw] 266 is, by the energizaticn and dener 'ization of magnet 281, returned to normal position, shown in the illustration. This (referring to Fig. 1) restores arms 199, 202. 211 and 215 to their normal positions Subscriber F now removes receiver 14 from the switch book. which causes hook lever 13 to move into engagement with anvil 12. and depres es and releases key 5 which. under the conditions just described. causes him to receive a signal that the desired subscribers line is busy. in the following manner: The depresion of key 5 causes the euergization of relay 72 in the manner already described. The energization of re lay 72 causes the energization of relay 145 in the manner described with reference to the operation of the connector switch. Ann 199 being at this time in its normal position,

shown in the illustration. the energization of relay 145 causes the energization of magnet 197 which causes an upward step of the shaft of the connector switch which allows contact spring 220 to engage anvil 219. This cuts busy back machine 191 into the receiving circuit of subscriber F and gives the characteristic busy signal, as soon as key 5 is released, over the following circuit: from the said busy back machine, through contact 2192'20, through contact 01-1-211, through contact 179--180, through condenser 176, through contact 129-128, through contact 13413'2, through limb H of the trunk circuit, through condenser 90, contact -H-i3, contact 58-55, over limb S of the telephone line and through the substation of subscriber F, returning over limb P of the line to battery 171. Upon receivingthe busy signal, subscriber F depreses simultaneously keys 2 and 5, replaces his receirer on the hook and releases the keys. This causes the release of second selector C and first selector A by the energiZ-ation and deenergization of their respective release magnets 1:20 and 2.8 in the manner hereindescribed.

Incase atrthe time the wipers of the connector switch are placed in. engagement with the contact points forming the terminals of the line of subscriber K, the saidline is idle, contact point 206 will be insulated from earth, and the depression and release of key 2 of subscriber F and the consequent energization and denergization of relay 192 will efi'ect the following circuit changes: Arm 199 is broughtinto engagement ,with contact point 201; arm 202mm engagement with contact point 5204, thereby establishing a ground connection to contact point 206 and its multiples and rendering the line of subscriber K busy with respect to other subscribers; arm 211 is brought into engage ment with contact point 213; and arm 215 into engagement with contact point 217. Release magnet 185 in this case fails to ,OP'. crate, owing to the absence of ground connection to contact 206 at the time subscriber F causes the encrgization of relay 146.

Subscriber F now depresses key 5 and releases it, establishing a How of current over limb P of the telephone line through relay 72 tobattery 81, causing the attraction of the armature of the said relay and establishing a flow of current over a path as follows: from ground 79. through contact between springs and 78, over limb H of the trunk circuit, through contact 165-166. through win w of relay 145 to battery 143, thereby energizing the said relay and causing the attraction of its armature, which establishes a path for the flow of current as follows: from ground 144, through contact 147-150. through contact 195-*19i, through contag 199- 201, through the winding of relay 178 to battery 214. Relay 178 is there by energized and attracts its two armatures 179 and 182, thereby cutting ringing generator 184 into the metallic circuit of the line of subscriber K and causing the bell of the said subscriber to ring.

Subscriber K in response to the call removes his telephone from the book, whereupon hook lever i3 engages anvil 19, establishing a path for a flow of current as follows: from the grounded side of battery 170, through one windin of relay 162, through winding 163 of re ay 172, through contact 180-179 (relay 178 being at this time deenergized) through contact'211213, contact 207-208, over limb P of the line of subscriber K, returning over limb S of the said line, through contact 210209, through contact HF-215, through contact 182183, through winding 16-! of relay 172, through the other winding of relay 162 to the active side of battery 170. Relay 172 is differentially wound and. under the above conditions, its core remains neutral or non-mag netized.

The above described flow of current causes the energization of relay 162 which attracts armature 165 into engagement with anvil 368, and armature 167 mto engagement with anvil 169. A path for the flow of current is thereby established as follows: from ground 154-, through winding 157 of relay 156, through contact 36S165, contact 129-128, contact 134-432, over limb H of the trunk circuit, through contact 78-75,

through contact 93-98, through the winding of relay 82, through contact 7776, over limb G of the trunk circuit, through contact 135137, contact 130-131, through the winding of relay 146, through contact 167169, through winding 158 of relay 156 and to the active side of battery 155.

The above described flow of current energizes relay S2 and attracts armature 84 into engagement with anvil 86, and armature 83 into engagement with anvil S7, at the same time opening the circuits, at the said armatures 84 and 83, of relays 71 and 72. The energization of relay 82 establishes a path for the flow of current as follows: from grounded side of batter; 99, through winding 91 of relay 97, through contact 86-84, through contact 42-41, contact 4038. ove limb P of the telephone line of subscribe F, through the talking circuit of the substation of F, returning over limb S of the telephone line, through contact 5558, through contact 43'14. through contact 8387, through the winding 92 of relay 97 to the active side of battery 99.

Subscribers F and K are now in conversation, their transmitters being energized by currents from batteries 99 and 170 respectively, throu h condensers 89 and 177 in one side of the talking circuit and through condensers and 176 in the other side of the talking circuit.

When the subscribers hare finished their conversation, each depresses keys 5 and 2 simultaneously and replaces his receiver. In case calling subscriber F has depressed simultaneously keys 5 and 2- a$ociated with his substation before subscriber K has depressed the keys associated with his substation, the release of the switching mechanisms employed in the connection between the two subscribers will be effected in the following manner: The depression of key 5 shunts winding 91 of relay 9?, while the simultaneous depression of key 2 continues a path for the How of current from battery through winding 92- of relay 9", over limb S of the telephone line to ground through contact Relay 9? is difierentially wound, its core becomes energized due to the unbalancing of its windings, and attracts armature 93 out or its normal engagement with anvil 98. This opens the circuit of relay S2. dei nergizing the said relay and allowing its armatures 84 and 8-3 to return to their normal positions in engagement with anrils 85 and S8, respectirely. This opens the circuit of relay 97 and causes its denergization. Limbs P and S of the telephone line of subscriber F being at this time both grounded at the substation, relays 71 and 72 are simultaneously energized by current flowing over thepaths already described with reference to the energizations of the said relays Their armatures being thereby simultaneously attracted, a flow of current results over the following path: from the grounded side of battery 81, through contact between springs '71 and 73, through contact 3029 of first mlector A, through contact through magnet 28 and to battery 22. Magnet '28 corresponds to magnet 281 in Fig. 2 and its energization places arms 264 and 265 in positions to accomplish the release and consequent return to normal of the mechanism of the first selector switch as soon as magnet 2-8 in Fig. 1 is denergized. The simultaneous energizations of relays 71 and ('2 established circuits as follows: from ground 79. through contact S076, over limb G of the trunk circuit, through contact 135-137, contact 130-431. through the winding of relay 146 energizing the said relay, through contact 1GT169. through Winding 158 of relay 156 md to the active side of battery 155: also a circuit from ground 79, through contact SO-78. over limb H of the trunk circuit, through contact 132-434, through contact 12S129, through contact 165-368, through winding 15? of relay 156 and to ground 151. Relay 1.56 being differentially wound. its winding 15? being short circuited, andcurrent at this time flowing inwinding l58,.t.he core of the said relay is magnctized and attracts armature 159 into engagement with anvil 160. This establishes a path for the flow of current as follows: from ground 161, through contact 159-160, through the winding of relay 145 and to battery 1-13, thereby energizing the said relay. Relays 145and 146 are now ener- The energization of relay 146 establishes a circuit from ground 144 through the winding of relay 192 to battery 196, whereby the said relay is energized and attracts its armature 195. Relay 145 being at this time energized, a path for the flow of current is established as follows: from ground 1-14, through contact 14T-150, througi contact 195193, through winding of magnet 185 and to battery 189. Magnet 185 is thereby ener ed and attracts its armature 186, establishing a. path for the How of current as follows: from ground 188, through contact 187186, through contact 119152 (relay 145 being at this time energized), through contact 125-424, contact 116118, through the winding of magnet- 120 to battery 119. Magnets 185 and 120 corresponding each to magnet 281 illustrated in Fig. 2, the energizations of said magnets 1 85 and 120 place the switching mechanisms, with which they are rcspec tirely associated, in 'pbsition to be released and returned to normal as soon as the said magnets are d'energized.

It will be noted that the continued energization of the three magnets, 185, 120 and 28, associated respectiyely with switches D, C and. A, is dependent upon the con tinued energization of relays 71 and 72 of trunk circuitB. Subscriber F releases the two keys 5 and 2 associated with his substation, opening the circuits of relays 72 and 71, 1115 receiver being at this time re placed on its hook. The resulting deenergization of the said relays opens the circuit of magnet 28, thereby denergizing the said magnet and causing the return of the mechanism of switch A to normal. The deenergization of the'said relay 71 also opens the circuits'of relays H6 and 156 axociated with switch D, and causes their denergization. The denergization of relay 1&6 opens the circuitof relay 192 causing the dener gization of the said relay; its armature 195 disengages anvil 193 opening the circuit of magnet 185 and causing the denergization of the said magnet which causes the return of the mechanism of switch D to its normal position. The denergization of magnet 185 opens the circuit of magnet 120 at contact point 1861S7 thereby causing the derr ergization of the said magnet 120 which causes the return of the mechanism of switch C to normal.

All apparatus at the central olfice, used in establishing the connection between subscribers F and K, has now been returned to normal and the two subscribers are in posi- Lions to make or receive further calls.

It will be noted that when subscriber F simultaneously depresses his two keys 2 and 5 and releases them. upon the termination of the conversation before subscriber ,K has simultaneously depressed the two keys associated with his substation, the act of subscriber K is of no elfect, the release of the entire apparatus being accomplished from the substation of subscriber F.

In case subscriber K depresses keys 2 and 5 associated with his substation in advance of the corresponding act of 'subscriber F, winding 183 of relay 172 is shunted, due to the fact that subscriber K grounds limb P of his telephone line. Current continues to {low from battery 170 through windin 164 of the said relay 172, over limb S 0 the telephone line of subscriber K to ground at the substation. Relay 172 being difl'erentially wound, its core is magnetized and its armature 173 is attracted to make engagement with anvil 174. A ath for the flow of current is thereby established from ground 175, through contact 173-174, through the winding of magnet 185 to battery 189. Magnet 133 is thereby energized and when subscriber K releases keys 5 and 2, removing grcund from the two limbs of his line at the substation, the circuit of relay 172 is opened, the relay denergized, and armature 173 resumes its normal position, opening contact 1741T3. This opens the circuit of magnet 135. causing the denergization of the said magnet which denergization causes the return of the mechanism of connector Switch I) to its normal position. The releasin of keys 2 and 5 by subscriber. K, his receiver being at this time replaced, opens the circuit of relay 16-2, causing the dencrgization of the said relay whereupon armatures 165 and 167 resume their normal positions in en gagement with anrils 166 and 16S, disengaging anrils 38Sand 1G9.

Relay 82 as ociated with B is denergized', due to the fact that its winding is come between the negative side of battery 143 and the negative side of battery 171 which batteries are of equal voltage, or which may be one and the same battery. The deenergization of relay 82 causes armaturcs Si and 83 to disengage anwils S6 and S7 rwpectively, and engage anrils S5 and 88 respectively, thereby opening the circuit of relay 97, cutting current from battery 99 out of circuit with the telephone line of subscriber F and reZ-stablishing the. bridges of relays 71 and T2 to be two strands of the talking circuit.

'hcn subscriber F simultaneously depresses keys 2 and 5 asociated with his sub station. and replaces his receiver on its book, relays T1 and 72 will be simultaneously energizcd in the manner already described. Magi-int '28 of first selector switch A will be energized in the manner already described with reference to the preceding disconnect operations. Relays 145 and 146 associated with connector switch D are simultaneously energized by currents over the previously traced paths established by the cnergization of relays 71 and 72 respectively. The energization of relay 146 establishes a previously traced path for the flow of current, energizmg relay 192 and attracting its armature 195 into contact with anvil 193. The energization of relay 145 establishes a path for the flow of current from ground 144 through contact 147150, through contact 195-1923, through the winding of magnet 185 to battery 189, causing the said magnet to be energized, whereby is established a path for the ow of current as follows: from ground 188, through contact 187-186, through contact 149152 (relay 145 being at this time energized), through contact 1251-2-l. through contact 116118, through the winding of magnet 120 to battery 119, thereby energizin the said magnet.

' en subscriber F releases keys 2 and 5, opening the line circuit at the substation, relays 71 and are deiinergized which deenergizations effect the denergizations of magnets 185, 120 and 28 in the manner described with reference to the operations of 9 release in the case in which subscriber F deressed keys 5 and 2 for releasing purposes fore subscriber K depressed the keys associated with his substation. The de'e'nergizations of magnets 120 and 28 cause the mcchanisms of second selector switch C and first selector switch A, respectively, to return to their normal positions While I show in Fig. 1, for purposes of illustration, a plurality of batteries, it is to be understood that they may be one and the same battery.

In applying my invention to trunking be tween exchanges, one battery at each ex change may be employed.

When in the claims I use the. expression, primary relay, I mean a relay associated with an automafic switch, having the function of initiating or causing a primary or first movement, or set of movements. of the switch with which it is associated. Relays 45, 101 and 145 in Fig. 1 are such relays. When I [1% the expression. secondary relay, I mean a relay associated with an automatic switch, having the function of initiating or causing a secondary or second movement, or set of movements. of the switch with which it is associated. Relays 49 and 102 are such relays. \Vhen I use the term, secondary connector relay, I mean a relay associated with a connector switch, having the function of preparing for, or rendering possible, a secondary or second movement, or set of movements. of the connector switch with which it is associated. Relay 146 is such a relay. When I use the term, primary trunk relay, I mean a relay having the function of controlling or causing the response of a rimary relay. Relay 72 is such a re ay. When I use the term, secondary trunk relay, I mean a relay having the function of controlling or causing the response of a secondary relay or secondary connector relay. Relay 71 is such a relay. When I use the term, control relay, I mean a relay having the function of including a source of current in a conversational circuit, or in a portion of such a circuit, to supply current for talking purposes. Relay 82 lS such a relay. When I use the term, release magnet, I mean a magnet having the function of disconnecting an automatic switch. Magnets 28, 1'20 and 185 are such magnets.

I claim 1. In a telephone exchange system provided with calling mechanisms at subscribeis stations and automatic switches at the central oflice for connecting subscribers lines, the combination of a telephone line connecting a substation with the central office, calling mechanism for said line at the substation, a trunk circuit in electrical connection with said line at the central ofiice, a source of current associated with said circuit, a primary trunk relay and a secondary trunk relay for said circuit responsive to said calling mechanm, an automatic switch at the central ofiioe, two conductors extending said trunk circuit to said automatic switch, a primary relay for said switch responsire to currents controlled by said primary trunk relay and a secondary relay for said switch responsive to currents controlled by said secondary trunk relay.

In a telephone exchange system pro vided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines, the combination of a telephone line connecting a substation with the central oiiice, calling mechanism for said line at the substation, a trunk circuit in electrical connection with said line at the central office, a source of current associated with said cir cuit, a primary trunk relay and a secondary trunk relay for said circuit responsive to said calling mechanism, an automatic switch at the central ofiice, two conductors extending said trunk circuit to said automatic switch, a primary relay for said switch responsive to currents controlled by said primary trunk relay, a secondary relay for said switch responsive to currents controlled by said secondary trunk relay and a release magnet for said switch responsive to cur renm adapted to be controlled by said circnitafter the telephone line is switched for conversation 3. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central oifice for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central office, calling mechanism for said line at the substation, a trunk circuit in electrical connection with said line at the central ofiice, a central source of current associated with said circuit, a primary trunk relay and a secondary trunk relay for said circuit responsive to said calling mechanis a connector switch at the central oliice, two conductors extending said trunk circuit'to said connector switch, a primary relay for said connector switch responsive to currents controlled by said primary trunk relay, a secondary connector relay responsire to currents controlled by said secondary trunk relay, mechanism controlled by said relays for making connection with :1 called subscribers line, and a release magnet for said connector switch responsive to currents adapted to be controlled by said circuit after the telephone line is switched for conversation.

4. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central olfice for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central office, calling mechanism for said line at the substation, a central source of current for operating urposcs, a trunk circuit at. the central 0 cc connected with said line, a primary trunk relay and a secondary trunk relay associated with said circuit responsive to said calling mechanism, a connector switch, a pair of conductors for said trunk circuit extended to said connector switch, and relays associated with said connector switch responsive to said trunk relays for causing the operation of said connector switch to place it in electrical connection with the line of a. called subscriber.

5. In a telephone system pron'ded with calling mechanisms at subscribers stations and automatic switches at the central otiice for connecting subscribers lines for couversation, the combination of a telephone line connecting a substation with the central office. calling mechanism at the substation. a first selector switch at the central nfice. connected to said line, a trunk circuit in clec trical connection therewith, a connector switch, two main conductors only for said trunk circuit extended to and in electrical connection with said connector switch, a primary trunk relay and source of current in circuit therewith responsive to said call- Eng mechanism, switching mechanism controlled by said relay, a primary relay forsaid connector switch responsive to said switchmechanism, a secondary trunk relay and'souz'ce of current in circuittherewith responsive to said callingmechanism,switching mechanism controlled bysaid relay, and a secondary connector relay for said consector switch responsive to said switching mechanim.

In a telephone system provided "with calling mechanisms at subscribers stations and automatic switches at the central oflice for connectingsubscribers lines for conversation, the combination of a telephone line connecting a substation with the central oflice. calling mechanism at the substation, a first mlector switch at the central olfice, connected to said line, a trunk circuit in electrical connection therewith, aconnector switch, two main conductors only for said trunk circuit extended to and in electrical connection with said connector switch, a primary trunk relay and source of current in circuit therewith responsive to said calling mechanism, switching mechanism controlled by said relay-ya primary relay for said connector switch responsive to said switching mechanism, a secondary trunk relay and source oi current in circuit therewith rcsponsire to said callin mechanism, switching mechanism controlled by said relay, a secondary connectorrelay for said connector switch respcnsire to said switching mechanisn and a release magnet for said connector switch responsire to said two switching mechanisms coo tively employed when the telephone line is switched'for conversation.

T. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conrersation, the combination of a telephone line connecting a substation with the central oilicc, calling mechanism at the substation, a first selector switch connected to said line, a trunk circuit in electrical connection therewith, a connector switch, two main conductors only for said trunk circuit extended to and in electrical connection with said connector switch, a primary trunk relay and source of current in circuit therewith re sponm've to said calling mechanism, switch- Eng mechanism controlled by said relay, :1 primary relay for said comector switch respousire to said switching mechanism, a secondary trunk relayinnd source of current in circuit therewith responsire to said calling mechanism, switching mechanism controlled by sa.d relay, a secondary connector relay for mid connector switch responsive to said switching mechanism, means for placing said connector switch in electrical comzco tion with a called subscribers line and mechanism for causing current to be supplied from a central source for talking purposes durinc conversation.

Sr 11 a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conversation. the combination of a telephone line connecting a substation with the central ofiice, calling mechanism at the substation, a first selector switch connected to said line, a trunk circuit in electrical connection therewith, a connector switch, two main conductors only for said trunk circuit extended to and in electrical connection with said connector switch, a primary trunk relay.and source of current circuit therewith responsive to said calling mechanism, switchieg mechanism controlled by said relay, 2. primary relay for said connector switch responsire to said switching mechanism, a secondary trunk relay and source of current in circuit therewith responsive to said calling mechanism, switching mechanism controlled by said relay, a secondary connector relay for said connector responsive to said switching mechanism, means for placing said connector switch in electrical connection with :1 called subscribers line, mechanism for causing current to be supplied from a central source for talking purposes durln conversation, and a release magnet for sai connector switch responsive to said two switch ing mechanisms coiiperativcly employed when the telephone line is sudtched for conversation.

9. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches atthe central olfice for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central office, calling mechanism for said line at the substation, a central source of current for operating purposes, a trunk circuit at the central ofiice connected with said line, a primary trunk relay and a secondary trunk relay associated with said circuit responsire to said calling mechanism, a connector switch, a pair of conductors for said trunk circuit extended to said connector switch, relays associated with said connector switch responsive to said trunk relays for causing the operation of said'connector switch to place it in electrical connection with the line of :1 called subscriber and means for sup plying current from a central source for talking purposes during conversation.

10. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central ollice for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the. central ollice, calling mechanism for said line at the substation, a central source of current for operatin purposes, a trunk circuit at l the central cc connected with said line, a

m responsive to said trunk relays for causing the operation of said connector switch to place it in electrical connection with the line of a called subscriber and a release magnet individual to said connector switch, adapted to be controlled by said trunk circuit after the telephone line is switched for conrersation.

11. In a telephone system provided with calling mechanism at subscribers stations and automatic switches at the central ofiice for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central office, calling mechanism for said line at the substation, a central source of current for operating purpos s, a trunk circuit at the central ofice connected with said line, a primary trunk relay and a secondary trunk relay associated with said circuit responsive to said calling mechanism, a connector switch, a pair of conductors for said trunk circuit extended to said connector switch, relays aociated with said connector switch responsive to said trunk relays for causing the operation of said connector switch to place it in electrical'connection with the line of a called subscriber, means for supplying current froma central source for talking purposes during conversation and a. release magnet individual to said connector switch, adapted to be controlled by said trunk circuit after the telephone line is switched for conversation.

12. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central oihoe for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central 0ffice, calling mechanism for said line at the substation, a central source of current for operating purposw, a trunk circuit at the central ofiice connected with said line, a pritrunk relay and a secondary trunk relay associated with said circuit responsive to said calling mechanism, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, relays associated with said selector switch responsive to said trunk relays for causing the operation of said selector switch to place said selector switch in electrical conugction with said connector switch and re lays associated with said connector switch responsive to said trunk relays when said switch is connected with said selector switch for causing the operation of said connector switch to place it in electrical connection with the line of a called subscriber.

13. In a telephone system provided with ca mechanisms at subscribers stations and automatic switches at the central ofiice for connecting subscribers lines for conversations, the combination of a telephone line connecting a substation with the central office, calling mechanism for said line at the substation, a central source of current for operating purposes, a trunk circuit at the central oliice connected with said line, a primary trunk relay and a. secondary trunk relay associated with said circuit responsive to said calling mechanism, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, relays associated with said selector switch responsive to said trunk relays for causing the operation of said solector switch to place said selector switch in electrical connection with said connector switch, relays associated with said cognector switch responsive to said trunk relays when said switch is connected with said selector switch for causing the operation of said connector switch to place it in electrical connection with the line of 2. called subscriber and means for supplying current from a central source for talking purposes during conversation.

14. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central oificc for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central oflicc, calling mechanism for said line at the substation, a central source of current for operating purposes, a trunk circuit at the central olice connected with said line, a primary trunk relay and a, secondary trunk relay associated with said circuit responsive to said calling mechanism, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, relays associated with said selector switch responsive to said trunk relays for causing the operation of said selector switch to place said selector switch in electrical connection with said connector switch, relays asociated with said connector switch responsive to said trunk relays when said switch is connected with said selector switch for causing the operation of said connector switch to place it in electrical connection with the line of :1. called subscriber, and release magnets individual to said selector switch and said connector switch respectirely, responsive to said trunk relays when the telephone line is switched for conversation.

15. In :1 telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central ollice for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central ollice. calling mechanism for said line at the substation, a central source of current for rpcrating purposes, a trunk circuit at the central oilice connected with said line, a primar trunk relay and a secondary trunk relay associated with said circuit responsive to said calling mechanism, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, relays asociated with said selector switch responsive to said trunk ielays for causing the operation of said selector switch to place said selector switch in electrical connection with said connector switch, relays asociated with said connector switch responsive to said trunk relays when said switch is connected with said selector switch for cursing the operation of said connector switch to place it in electrical connection with the line of a called subscriber, means for supplying current from a central source for talking purposes during conrersation and release magnets individual to said selector switch and said connector switch re spectively, responsive to said trunk relays when the telephone line is switched for conversation. i

16. In a telephone system providedwith calliing mechanisms at subscribers stations and automatic switches at thegoentral oilice for connecting subscribers lines fonconrersation, the combination of a'telephone. line connecting a substation withhthe tral o-Eice, calling mechanism for said line at the substation, a central source of xcurrent'lfor operating purposes, an automatic {switchindiridual to said line at the central iifiicg'a trunk circuit at the central ollice, electromagnetic means for operating responsive to said calling mechanism ted to place said line in electrical co'nnectidn with said circuit, electromagnetic switching cleric-es associated with said circuit responto said calling mechanism when said :1 nit is connected with said line, a selector switch, a pair 05 conductors for said trunk circuit extending to said selector switch, a connector switch. electromagnets associated with said selector switch responsive to said switching dewlces for causing the operation of said selector switch to place said selector switch in electrical connection with said connee-tor switch. and electromagncts as ociated with said connector switch responsive to said switching devices when said switch is connected with said selcctor switch for causing the operation of said connector switch to plage it in electrical connection with the line of a glillled subscriber.

17. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central office for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central office, calling mechanism for said line at the substation, a central source of current for operating purposes, an automatic switch individual to saidline at the central oflice, a trunk circuit at the central office, electromagnetic means for operating said switch responsive to said calling mechanism adapted to place said line in electrical connection with said circuit, electroma etic switching devices associated with sai circuit responsive to said calling mechanism when said circuit is connected with said line, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, electromagnets associated with said selector switch responsive to said switching devices for causing the operation of said selector switch to place said selector switch in electrical connection with said connector switch, electromagnets asdociated with said connector switch responsive to said switching devices when said switch is connected with said selector switch for cans ing the operation of said connector switch to place it in electrical connection with the line of a called subscriber and means for supplying current from a central source for talkin purposes during conversation- 18. n a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central of- .fice, calling mechanism for said line at the substation, a central source of current for operating purposes, an automatic switch individual to said line at the central oflioe, a trunk circuit at the central oifiee, electro giagnetic means for operating said switch responsive to said calling mechanism adapted toplace. said line in electrical connection with aid circuit, electromagnetic switching devices associated with said circuit responsive to said calling mechanism when said circuit is connected with said line, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, electromaguets associated with said selector switch responsive to said switching devices for causing the operation of said selector switch to place said selector switch in electrical connection with said connector switch, electromagncts associated with said connector switch responsive to said switching devices when said switch is connected with said selector switch for causing the operation of said connector switch to place it in electrical connection with the line of :1 called subscriber, and release n1ech anism for disconnecting said automatic switch, said selector switch and said connector switch, responsive to said switching devices when the telephone line is switched for conversation.

19. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conversation, the combination of a telephone hne connecting a substation with the central office, calling mechanism for said line at the substation, a central source of curreng1 for o eratin urposes. an automatic switc indi vidual tb said line at the central oflice, a trunk circuit at the central oflice, electromagnetic means for operating said switch responsive to said calling mechanism adapted to place said line in electrical connect on with said circuit, electrom 'netic switching devices associated with sai circuitresponsire to said calling mechanism when said circuit is connected with said line, a selector switch. a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, elect-romagnets associated with said selector switch responsive to said switching devices for causing the operation of said selector'switch to place said selector switch in electrical connection with said connector switch, electromagnets associated with said connector switch onsive to said switching devices when sai switch is connected with said selector switch for causing the operation of said connector switch to place it in electrical connection with the line of a called subscriber, means for supplying. current from a central sourcefoc talking purposes during conversation and release mechanism for disconnecting said automatic switch, said selector switch and said connector switch, responsive to said switching devices when the telephone line is switched for conversation.

20. In a telephone exchange system provided with calling mechanisms at subscribers stafions and automatic switches at the central office for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of calling mechanism for said line at the substation, a pair of relays at the enchange adapted to be controlled by means of said mechanism, and a selector switch and a connector switch adapted to be succemively operated, responsive to said relays, in establishing desired connections.

21. In a telephone exchange system pro vided with calling mechanisms at subscribers stations and automatic switches at the central ofice for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with thenexchange, of calling mechanism for said line at the substation, a pair of relays at the be controlled exchange adapted to be controlled by means of said mechanism, a selector switch and a connector switch adapted to be successively operated, responsive to said relays, in establishing desired connections and mechanism adapted to be operated responsive to said relays when disconnection is desired for releasin said switches.

22. n a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central oilice for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of calling mechanism for Said line at the substation, a pair of relays at the exchange adapted to be controlled by means of said mechanism, a selector switch and a connector switch adapted to be successively operated, responsive to said relays, in establishing desired connections, mechanism adapted to be operated responsive to said relays when disconnection is de sired for releasing said switches, a central source of current and a relay at the exchange adapted to include said source in circuit with connected lines to supply current thereto for conversational purposes.

23. In a-telephone exchange system pro vided calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers Lines for conversation, the combination with a telephone line connecting a substation with theje'xchange, of calling mechanism at the substation, a pair of relays at the exchangeiiid'apted to becontrolled by means of a selector switch and a connector switch adapted to perform succesive switching operations in connecting said line with adesired line, electromagnets for operating said selector switch adapted to be controlled by'said relays and elect-romagnets for operating said connector switch adapted to by said relays 24. In a telephone exchange system prorided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conversation, the combination with a telephone Line connecting a substation with the exchange, of a pair of electroma; nets at the exchange adapted to be controlled from the substation, conductors associated with said electromagnets, and armature a paratus controlled thereby adapted to trans mit switching currents over said conductors. a selector switch. electromagncts for operat ing said switch in circuit with said conduc tors and adapted to be operated by said our rents, a connector switch, elecrromagnets for operating said switch. and apparatus for cutting said conductors out of circuit with the electromagnets of said selector switch after said electi'omagnets are operated, and

for cuttingthem into circuit with the electromagnets of said connector switch to render said switch controllable by currents trans mitted over said conductors.

In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central oilice for connecting subscribers lines for conversation, the combination with a telephone line extending from a substation to the exchange, of calling mechanism at the substation adapted, under control of the subscriber, to effect the transmission of currents over the line, electromagnets at the exchange adapted to be controlled by means of said mechanism, conductors associated therewith and switching apparatus controlled by said electromagnets adapted to transmit currents over said conductors, a selector switch, contacts included in the mechanism thereof for continuing the circuit of saidfline to a desireddline, alpddelectroma uets or operating sai switc a apt ed to be controlled by currents transmitted over said conductors by said apparatus after said selector switch is operated.

26. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central ofiice for connec subscribers lines for conversation, the com ination With a telephone line connecting a substation with the exchange, of mlling mechanism at the substation, relays at the exchange adapted to be controlled by means of said mechanism, a selector switch and a connector switch adapted to perform successive switching operations inconnecting said line with a desired line, electromagnets for operating said selector switch adapted to be controlled by said relays, electromagnets for operating mid connector switch adapted to be controlled by said relays and a, central source of current and branches adapted to supply cur rent. therefrom to subscribers lines for conversational p 2T. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central oliice for connecting subscribers lines for conversation, the combination with a' telephone line connecting a substation with the exchange, of calling mechanism at the substation, relays at the exchange adapted to be controlled by means of said mechanism, a selector switch and a connector switch adapted to perform successive switching operations in connecting said line with a desired line, electromagnets for operating said selector switch adapted to be controlled by said relays, electromagnets for operating said connector switch adapted to be controlled by said relays, a central source of current and branches-adapted to supply current therefrom to subscribers lines for conrersational purposes and release magnets for disconnecting said switches adapted to be controlled from the substation.

:28. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central office for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of electromagnets at the exchange adapted to be controlled from the substation, conductors associated with, and armature apparatus controlled by said electromagnets adapted to transmit switching currents over said conductors, a selector switch, electromagnets for operating said switch in circuit with said conductors, and adapted to be operated by said currents, a. connector switch, electromagnets for operating said switch, apparatus for cutting said conductors out of circuit with the electromagnets of said selector switch, after said electromagnets are operated, and for cutting them into circuit with the electromagnets of said connector switch to render said switch controllable by currents transmitted over said conductors and a central source of current and bridges adapted to supply current therefrom to subscribers lines for conversational purposes.

29. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central ofiice for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of electromagnets at the exchange adapted to be controlled from the substation, conductors associated with, and armature apparatus controlled by said electromagnets adapted to transmit switching currents over said conductors, a selector switch, electromagnets for operating said switch in circuit with said conductors, and adapted to be operated by said currents, a connector switch, electromagnets for operating said switch, apparatus for cutting said conductors out of circuit with the electromagnets of said selector switch, after said electromagnets are operated, and for cut ting them into circuit with the electromagnets of said connector switch to render said switch controllable by currents transmitted over said condpctors, a central source of current and bridges adap ed to supply current therefrom to subscribersline: for conveisational purposes -ud relc e magnets for salt: switches-115a ed to d uncut them under substatior con .iol.

30. In a telephone exchange system pro \ided with calling mechanisms at subscriir ers stations and automatic switches at the cental oliice for connecting subscribers lines for conversation. the combination with a telephone line extending fZ'LlD a subslacontrolled by currents transmitted over said conductors by said apparatus, a connector switch, contacts included in the mechanism thereof for continuin the circuit of said line to a desired line, e ectromagnets for operating'said' switch adapted to be controlled by currents transmitted over said conductors by said apparatus after said selector switch is operated and release magnets for said switches adapted to be operated under substation control.

31. In a telephone exchange system prorided with callingmechanisms at subscribezs' stations and automatic switches at the central olfice for connecting subscribers lines for conversation, the combination with a calling subscribers line connecting the substation with the exch e, of calling mechanism for the line at esubstat-ion, relays at the exchange adapted to be controlled by means of said mechanism, a called subscriber's line and a selector switch and a connector switch at the exchange adapted to succemively cofiperate with said relays in connecting said lines.

In a telephone exchange system provided with calling mechanisms atsubscribers stations and automatic switches at the central ofice for connecting subscribers lines for conversation, the combination with a calling suhscribers line connecting the substation with the exchange of calling mechanism for the line at, the substation, relays at the exchange adapted tobecontrolled by means of snid mechanism, a called subscribers line, a selector switch and a connector switch at the exchange adapted to successively cofiperate with said relays in connecting said lines and a central source of current adapted to supply current to subscribers lines for purposes of conversation- 33. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central ollice for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of a relaj at the exchange adapted to be controlled from the substation, :1 selector switch, an electromagnet, adapted to effect primary switching movements of said switch, responsive to said relay, a connector switch, an elect-romagnet, adapted to eliect primary switching movements thereof, responsive to said relay, :2. second relay at the exchange adapted to be controlled from the substation and electromagnets for said switches respectively, adapted to permit secondary switching movements of said switches, responsive to said second relay.

34. In a telephone exchange system provided with calling mechanisms at subscribems stations and automatic switches atthe central ofiice for connecting subxribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of a relay atthe exchange adapted to be controlled from the substation, a selector switch, an electromagnet, adapted to efl'ect primary switching movements of said switch, responsive to said relay, a connector switch, an electromagnct, adapted to effect primarv switching movements thereof, responsive to said relay a second relay at the exchange adapted to be controlled from the substation, electromaguets for said switches respectively, adapted to permit secondary switching movements of said switches, responsive to said second relay and apparatus for restoring said switches to normal adapted to be controlled from the substation,

35. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central ofiice for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of a relay at the exchange adapted to be controlled from the substation. a selector switch, an elect-1o magnet, adapted to effect primary switching movements of said switch, responsive to said relay, a connector switch, an electro magnet. adapted to effect primary switching movements thereof, responsive to said relay, :1 second relay at the exchangeadapted to be controlled from the substation, electromagnets for said switches respectively, adapted to permit secondary switching moi'ements of said switches, responsive to said second relay, apparatus for restoring said switches to normal. adapted to be controlled from the substation and a central source of current and bridges adapted to supply current therefrom for operating and conversational purposes.

36. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central office for connecting subscribers lines for con versatiou. the combination with a calling subscriber's line connecting the substation with the exchange, of calling mechanism for said line at the substation, a

central source of current for operating purposes, a relay at the evchange adapted to be controlled by said mechanism, a called subscribcrs line, a selector switch and a connector switch adapted to perform successive switching operations in connecting said subscribers lines, electromagnets for said switches respectively, adapted to efi'ect primary switching movements thereof, responsive to said relay, a second relay adapted to be controlled by said calling mechanism and electromagnets for said switches respectively, adapted to permit secondary switching movements thereof, responsive to said relay.

37. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conversation, the combination with a calling subscribers line connecting the substation with the exchange, of calling mechanism for said line at the substation, a central source of current for operating purposes, a relay at the exchange adapted to be controlled by said mechanism, :1 called subscribers line, a selector switch and a connector switch adapted to perform successive switching operations in connecting said subscribers lines, elcctromagnets for said switches respectively, adapted to eflect primary switching movements thereof, responsive to said relay, a second relay adapted to be controlled by mechanism, electromagnets for said switches respectively, adapted to permitsecondaryswitching movements thereof, 7 've to mid relay and bridgs adapted to supply current from a central source to subscribers lin for purposes of conversation,

38. Ina telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central ofiice for connecting subscriber's lines for conversation, the combination with a calling subseribers line connecting" the substation with the exchan of calling mechanism for said line at the substation,

a central source of current for operating urposes. a relay at the exchan e ada ted ll be controlled by said mechanis in, a p subscribers line, a selector switch and a connector switch adapted to perform 'succesive switching operations in connecting said subscribers lines, electromagnets for said switches respectively, adapted to efict primary switching movements thereof, responsive to said relay, a second relay adapted to be controlled by said calling mechanism, electromagnets for said switches respec tively adapted to permit secondary switching movements thereof, responsive to said relav, bridges adapted to supply current fronr a central source to subscribers lines for purposes of conversation and release magnets forsaidswitches adapted to be controlled from the substations.

39. In a telephone exchange system, the combination of a first selector, a second selector, a repeater interposed between the first and second selectors, a connector, a calling subscribers line, :1 called subscriber's line, a calling subscribers impulse transmitter for operating the said selectors and connector, and for operating said repeater, means in the connector for closin a trunk release circuit through the secon selector, means in the repeater for closing a trunk release circuit back thro h the first selector, andmeans for supplyin electrical current for operating the sari selectors and connector and repeater.

40. In a telephone exchange system, the combination of a first selector, :1 second selector, a repeater interposed between the first and second selectors, a connector, :1 calling subscribers line, :1 called subscribers line, a calling subscribers impulse transmitter for operating the said selectors and connector, and for operating said repeater, means in the connector for closing a trunk connector, and for operating said repeater, means in the repeater for do a trunk release circuit back through th ia first selector, a battery for operating the first selector and the repeater, and another battery for operating the second selector and the connector 41.111 a telephone exchange system, the combination of a calling subscribers line, an automatic switch individual thereto, other automatic switches, a called subscribers line, bridged relays for all of said automatic switches, means for cutting oil the relay bridges of one or more of said switches, a repeater inter between two of said antomatic swit es, line relays for said repeater, adapted to remain bridged across the circuit, and release devices for said automatic switches controlled by the relays of 11 said remaining bridges.

42. In a telephone exchange system, the combination of a telephone line circuit extending between calling and called substations, an automatic switch provided with relay means temporarily disconnected from said circuit, a repeater, means in said repeater for repeating or relaying electrical impulses from one portion of said circuit to another, a trunk release circuit extendin between the automatic switch and the repeater, and means in said repeater for closing said trunk release circuit.

43. In a telephone exchange system, the combination of a plurality of automatic switches, arepeater provided with line relays for successively controlling said automatic switches, a subscribers individual switch, a release circuit extending between the individual switch and the repeater, 

